1. Field of the Invention
The present invention relates to a coal upgrade plant and a method for manufacturing upgraded coal.
2. Description of Related Art
Since low ranking coal such as sub-bituminous coal and lignite has a lower carbonization degree and a higher water content than high ranking coal, a calorific value per unit weight is lower. However, since there are abundant deposits of low ranking coal, the low ranking coal is desired to be effectively used. Thus, various coal upgrading techniques have been studied in which the calorific value of the low ranking coal is increased by performing pyrolysis after drying the low ranking coal, and upgraded coal is deactivated so as to prevent spontaneous combustion during transportation or storage (e.g., Japanese Unexamined Patent Application, Publication No. 2014-31462 (hereinafter referred to as JPA 2014-31462)).
JPA 2014-31462 discloses that pulverized coal is fed into a pyrolysis furnace, and mercury-based substances (HgS, HgCl2 or the like) contained in a pyrolysis gas generated when coal is pyrolyzed are adsorbed to the pulverized coal and discharged outside of a system in order to prevent an increase in the concentration of mercury in pyrolyzed coal with the mercury-based substances being re-adsorbed to the pyrolyzed coal. The pulverized coal adsorbing the mercury-based substances is incinerated in a combustor to produce a combustion gas. The combustion gas is released to the atmosphere through a denitration apparatus, an electric dust collector, and a desulfurization apparatus after heating a pyrolyzer. While the mercury-based substances generated in the pyrolysis furnace are incinerated in the combustor together with the pulverized coal adsorbing the mercury-based substances as described above, only the pulverized coal is incinerated, and the mercury remains as a gas in the combustion gas. Thus, the remaining gaseous mercury is removed in the denitration apparatus and the desulfurization apparatus.
However, even when the mercury existing in a gaseous state in the combustion gas is removed in the denitration apparatus and the desulfurization apparatus, the mercury may not be removed to a desired concentration or less.
The present invention has been made in view of such circumstances, and an object thereof is to provide a coal upgrade plant and a method for manufacturing upgraded coal capable of removing mercury generated from the coal upgrade plant.